The present invention relates to an automatic ultrasonic flaw detector for detecting the inner flaw or defect of a molded material made of plastic, composite material or metal.
For example, a molded material formed of composite material has an L-shaped, T-shaped or H-shaped cross section. The molded material is formed along the longitudinal direction.
In order to inspect any flaw or defect existing within the molded material, an ultrasonic flaw detecting technology is utilized.
The ultrasonic flaw detecting technology relates to propagating ultrasonic waves onto the surface of a molded material through medium such as water, converting the sonic wave reflected from the front surface of the molded material, the flaw existing within the material, and the back surface of the material into electric signals, and thereby detecting the inner conditions of the molded material.
According to another method (the through transmission method), the inner flaw may be detected by propagating ultrasonic waves from one side of the molded material placed under water, and receiving the transmitted sonic waves.
FIG. 9 shows the principle of an ultrasonic flaw detector utilizing the through transmission method.
Water W is filled inside a tank 10, and a molded material P1, which is the object of inspection, is positioned inside the tank.
Ultrasonic wave V1 is propagated toward the molded material P1 from a transmission search unit 20. A reception search unit 30 positioned to oppose to the unit 20 receives the transmitted sonic wave V2, and detects flaw.
According to such device, the transmission search unit 20 and the reception search unit 30 must be operated in synchronism. Moreover, the transmitted ultrasonic wave V1 must be converged to concentrate the energy, and therefore, it is difficult to detect the flaw formed to a corner portion A1 and the like of the molded material P1.
Therefore, a flaw detector utilizing a reflection method is provided.
Water W1 is filled inside a tank 10, and a molded material P1 is placed inside the tank 10. On one side wall of the tank 10 is positioned a plurality of search units 40, which are for transmitting and receiving ultrasonic waves.
Similarly, a plurality of search units 50 are positioned to the bottom of the tank 10, which are for transmitting and receiving ultrasonic waves.
FIG. 11 is an explanatory view showing the result of inspection performed according to the above flaw detector.
The ultrasonic wave V1 transmitted from the search unit 40 is reflected by the front surface S1 and the back surface b1 of the molded material P1, and a waveform as shown in FIG. 11 is drawn on an oscilloscope O1.
In advance, a normal (good) back surface reflection level L1 is set within the range of a gate G1 as the back surface range width, using a sample.
FIG. 11 (A) shows the reflected wave of the solid (good) portion of the molded material P1. The reflected wave EB1 reflected by the back surface B1 exists above the set level L1 within the gate G1, and therefore, the inspected portion is determined to be acceptable.
FIG. 11 (B) shows the state where a void H1 so-called porosity is formed within the molded material P1. When such a void H1 exists, the reflected wave EB1 is damped, and the level will not reach the set level L1. As a result, the inspected portion is determined to be unacceptable.
FIG. 11 (C) shows the state where an exfoliated portion F1 so-called a delamination exists near the back surface B1 of the molded material P1. If the molded material P1 is manufactured by press forming plural sheets of laminated FRP films, delamination portion F1 is likely to appear within the material.
When such defect exists, however, the reflected wave EF1 from the delamination portion F1 may exceed the set level L1 within the gate portion G1 set to the position corresponding to the back surface B1, and the inspected portion may be determined to be acceptable.
Especially when the thickness of the molded material is small, such problem occurs.
Therefore, the present invention aims at solving the above problems of the prior art by providing a device capable of detecting the flaw existing within the object molded material correctly, even if the molded material is formed of composite material.
The automatic ultrasonic flaw detector according to the present invention comprises, as basic means, a flaw detection chamber filled with water and having an opening portion through which a molded material being the object of inspection travels; an ultrasonic search unit positioned within the chamber to oppose to one surface of an object portion of inspection of the molded material; an ultrasonic reflector plate positioned to oppose to said ultrasonic search unit and to have a predetermined distance from the other surface of said object portion of inspection; and an inspecting means for comparing the reflected signal of ultrasonic waves with the signal from a solid portion.
The detector further comprises rollers for gripping and sending the molded material into the flaw detection chamber, and bellows equipped to the opening portion of the flaw detection chamber through which the molded material travels, so that water within the chamber is prevented from leaking.
The reflector plates are formed as a unit removably placed within the flaw detection chamber, and the unit of reflector plates is divided into two parts with its boundary set along the opening portion of the flaw detection chamber.